Research of CO-Soluble Surfactants for Enhanced Oil Recovery: Review and Outlook.

CO foam injection has been shown to be effective under reservoir conditions for enhanced oil recovery. However, its application requires a certain stability and surfactant absorbability on rock surface, and it is also associated with borehole corrosion in the presence of water. Adding surfactants to CO can enhance the interaction between CO and crude oil and control the CO mobility, thereby improving the performance of CO flooding. This paper presents a review of the research of CO-soluble surfactants and their applications. Molecular dynamics simulation is introduced as a tool for analyzing the behavior of the surfactants in supercritical CO (scCO). The applications of CO-soluble surfactants, including CO thickening, reducing miscibility pressure, and generating supercritical CO foam, are discussed in detail. Moreover, some opportunities for the research and development of CO-soluble surfactants are proposed.